Depending on the kind of person you are, plans for things are going to be either completely familiar to you, somewhat familiar to you, or not at all familiar to you. While it is not necessary to have a completely detailed business plan before you start (especially if your business is online, but also if it happens to be offline), there are some things that you should generally be aware of at the very least before you take towards building up your business.
The first of those things has to do with figuring out the topic that your business is going to be on. This is not a topic in terms of something that a book needs to have, but rather a topic in terms of what your business is going to be about. For example, if a person wanted to open a restaurant, then there would be a culinary topic to their business. If someone wanted to blog, then the topic would be whatever they wanted to blog about. There are a number of different topics available out there today and choosing one for your business is perhaps the most important thing you can plan ahead of time.
Now, when most people are choosing the topic of their business, they tend to use one of two methods. They will either choose a business topic that they are very familiar with, love doing and would really have no problem doing for free, or alternatively they will choose a business topic that they think would generate a lot of interest in the demographics that they can reach. If you are on the internet, then the demographic you can reach is endless, whereas if you are off the internet, then you need to be aware of the people that live near wherever your business happens to be.
While these two methods of business topic choosing both have their ups and their downs, neither one is inherently better than the other. There are certain situations (i.e. blogging for a profit) where one might be obviously indicated as being the better one, but for the most part you can get along choosing either of those two things.
That idea brings us to the big question; how do you know which one of the two methods you should choose? Well, it once again depends on the type of person you are. If you are a free spirit, not really interested in too much planning and willing to take a chance just to see where it takes you, then choosing something that appeals to you and that you would do for free might be the way to go. If you are the meticulous type and are good at keeping things organized, then it would seem that going for the more likely profit would be a better idea. It largely depends on you and while neither of the two choices is wrong, it is very important that you are confident in the choice you make.